core

### Constructing a Primary Datum Plane

Prior to version 2019 R1 the Primary Datum Plane was referred to as the "Tangent Plane" or "High Point Plane".

PC-DMIS does not currently support the ASME Y14.5-2009 tangent plane modifier.

You can construct a plane that is external to the material (tangent to the peaks or the high points) on a surface. You can then use this feature as a datum in alignments or dimensions. Do not dimension a primary datum plane. That is not its purpose. You should use it only as a datum feature.

To construct a Primary Datum plane:

1. Select Insert | Feature | Constructed | Plane to display the Construct Plane dialog box.

2. From the list where it says Auto, select the Primary Datum option.

3. Select the input features from one of these options:

- Three or more features (you may use any feature type).

- Any single feature set. For information on feature sets, see "Constructing a Set of Features".

- Any plane feature.

- Any scan.

4. From the Math Type area, from the top list, select a math type. For information on these math types, see "Primary Datum Plane Math Types":

- CONSTRAINED_L1

- CONSTRAINED_L2

- CONSTRAINED_MINMAX

5. From the bottom list in the Math type area, select either BF (Best Fit) or BFRE. (Best Fit Re-Compensate). For information on Best Fit planes, see "Constructing a Best Fit or Best Fit Recompensate Plane".

6. Click the Create button.

- First, PC-DMIS constructs a Best Fit plane from the input features according to the math type.

- Next, PC-DMIS rotates to the Best Fit plane.

- Then, PC-DMIS finds the optimal primary datum plane from the highest points.

The Edit window command line for this option reads:
CONSTR/PLANE,PRIMARY DATUM,feat_1, feat_2, feat_3,…

More:

Primary Datum Plane Math Types